Gene Mutation

Question 1

What is mutation and how does it relate to evolution?

Answer 1

Mutation is a change in the genetic sequence maybe altering the phenotype. This is how genetic change occurs. Natural selection preserves the best combinations for its environment. This is evolution.

Question 2

Somatic Mutation

Answer 2

Occurs only in descendants of that cell (mitosis) - clone

Question 3

Germline Mutation

Answer 3

Transmitted through gametes (meiosis - 1/2 of descendants are mutated)

Question 4

When talking about results in gene mutation what generation are we referring to?

Answer 4

Second

Question 5

Base substitution

Answer 5

Transition: pur-pur or pyr-pyr
Transversiton: pur-pyr

Question 6

Insertions/Deletions/Frameshift Mutations

Answer 6

Caused by strand slippage or unequal crossing

Question 7

Tautomeric Shift

Answer 7

Results in a transition mutation
T and G -> O=CH-NH3 -> OH-CH=N
C and A -> NH2-CH=N -> N=CH-NH3

Question 8

Expanding Nucleotide Repeats

Answer 8

Increase in number of copies of sets of nucleotides - repeat copy number is in flux with each round of replication (can expand or contract)

Question 9

Expanding Nucleotide Repeats - Inside coding sequence

Answer 9

Huntington’s

Question 10

Expanding Nucleotide Repeats - Outside coding region

Answer 10

Fragile X

Question 11

Forward mutation

Answer 11

wild type -> mutant

Question 12

Reverse

Answer 12

mutant -> wt

Question 13

missense

Answer 13

AA->diff AA (base substitution)

Question 14

Nonsense

Answer 14

Stop (base sub)

Question 15

silent

Answer 15

changes to same AA

Question 16

neutral

Answer 16

AA change with no observable change (gly-ala)

Question 17

loss of function

Answer 17

CF

Question 18

gain of function

Answer 18

ex. larva growing legs where antenna are

Question 19

conditional

Answer 19

temp sensitive

Question 20

lethal

Answer 20

death

Question 21

suppressor

Answer 21

2nd site mutation that hides effect of 1st mutation (rescue)

Question 22

suppressor - intragenic (within gene)

Answer 22

may restore original AA

Question 23

suppressor - intergenic

Answer 23

2nd mutation is a gain of function that binds to stop codon

Question 24

DNA damage is caused by internal factors generated by what normal metabolic processes inside the cell?

Answer 24

1. H2O (hydrolysis - H2O2)
2. O2 (oxidation)
3. alkylating agents

Question 25

Spontaneous Mutation

Answer 25

occur under normal circumstances as a result of internal factors

Question 26

Spontaneous Mutation - deletions/insertions

Question 27

Spontaneous Mutation - depurination - break of what bond between 1’C of deoxyribose sugar? This creates what kind of site? What base is filled in?

Answer 27

break of covalent bond between 1’C of deoxyribose sugar creating apurinic site (A is filled in)

Question 28

Spontaneous Mutation - deamination- loss of what base? What does it give rise to? What kind of transition?

Answer 28

loss of C group giving rise to U which pairs with A->T. This leads to a C->T transition

Question 29

Spontaneous Mutation - mispairing (Wobble)

Answer 29

shift in backbone (2 H bonds) - like tautomeric shift but doesn’t use rare forms. G and T -> O=CH-NH3, C and A -> NH2-CH=NH

Question 30

Induced mutations

Answer 30

Result of an exposure to external factors (environment chemicals/radiation). Increases mutation rate above spontaneous rate (mutagen)

Question 31

Induced mutations - Base analogs

Answer 31

5Bru base analogue of T (pairs with A and G)
or
2-aminopurine base analogue of A and can mispair with C

Question 32

Induced mutations - alkylating agents- what group does it add? Example? What kind of trnasition?

Answer 32

adds methyl/ethyl group (mustard gas) G->A transition

Question 33

Induced mutations - deaminating agents - What acid? What transition? What base pair?

Answer 33

nitrous acid
C->T transition
U::A base pair

Question 34

Induced mutations - hydroxylamine - What group is added to C? What does this increase? What transition is this?

Answer 34

adds hydroxyl group to C which increases occurrence of rare tautomers that pair with A
C->T transition

Question 35

Induced mutations - Oxidative Radicals

Answer 35

hydrogen peroxide (transversions)

Question 36

Induced mutations - intercalating agents - What is the result of sandwhiching induced mutation between adjacent base pairs? What mutation is this from? Example?

Answer 36

sandwich between adjacent base pairs distorting helix (insertions/deletions/frameshift) ex. ethidium bromide

Question 37

Induced mutations - radiation - x rays (ionization)

Answer 37

breaks phosphodiester bonds = double stranded breakage

Question 38

Induced mutations - radiation - UV

Answer 38

induces chemical bonds between two adjacent pyrimidines (thymidine dimers)